Wednesday's forecast calls for "rain and showers" in D.C. Aren't those, like, the same thing? (No!)

What is falling from the D.C. skies today,

It's a dismally damp day in D.C., and the weather forecast reflects that: Expect "periods of rain and showers" throughout the afternoon and evening. But wait – isn't it a little redundant to say that? Don't rain and showers amount to the same thing, meaning wet stuff that falls from the sky and sometimes from the roofs of Metro cars, too?

Actually, no. The key difference between the two terms is that rain is a form of precipitation, whereas showers is one of several terms used to describe what the precipitation is doing. "Showers" falls into the same category as "patches," "shallow" and "freezing," words you can stick in front of "rain" or "snow" to give people a better idea of the nature of the precipitation outdoors. Take a look at this table showing the METAR aviation codes for rain (RA) and showers (SH) among other things:

"Showers," however, does imply a few things about the rain. Ready to geek out over weather terminology? LET'S DO THIS.

Rain's formal definition according to NOAA's glossary is liquid precipitation that "falls to earth in drops more than 0.5 mm in diameter." (Anything smaller than 0.5 mm is considered "drizzle." And don't even get me started on mist.) The word "rain" suggests that the precipitation is steady and continuous.

Showers, though, is rain that 1) starts and stops, sometimes suddenly, and 2) undergoes rapid changes of intensity. In other words, showers are the kind of rain that will catch you outside without an umbrella and make you curse your local meteorologist for not providing fair warning about the weather. But he or she did warn about it by using the descriptor "showers."

Interestingly enough, many people seem to have an innate understanding of the basic differences between the terms. In a 1996-1997 survey by the Juneau office of the National Weather Service, people chose the correct definitions for "rain" and "showers" 46 percent of the time, and 77 percent correctly inferred that "showers" start and stop abruptly. Only 6 percent of the survey takers felt there was no disparity between the two. Says the NWS of these results:

Based on the results of this question, when a "rain" or "showers" forecast is written, over half of the general public does not understand the precise meaning of the forecast; but since more than three-quarters of the respondents knew (or guessed) that showers imply precipitation that start and stops, use of the term "showers" does seem to convey more detail to the user. On the other hand, a forecast that says, "rain changing to showers," may be unnecessarily detailed considering the exact difference between rain and showers is not widely understood. We did receive comments on this particular wording; one of which stated, "Rain changing to showers... to me either it's going to rain or not. Rain is rain. What's the difference?"